Is That Your Final
Antler?

During December, the antlers of mule and
white-tail deer,
moose and
stag caribou fall to the ground, making it common to see animals with just a
single antler. Elk retain their
antlers throughout the winter, only shedding them with the onset of spring.
The antlers don't stay on the ground for long because the local
rodent population makes short work of this high quality source of calcium.

While the antlers are impressive
to look at, they are even more impressive on an evolutionary scale.

Why Grow Antlers?

In every
animal population, strategies have developed to help ensure the strongest
individuals get the greatest opportunity to mate. While antler size has
no bearing on the age of the individual, it IS a great indicator of the health
of the animal. Antlers are renewed each year meaning the stags need to find a
large source of calcium to supply the antler growth. With a diet of green
vegetation, one might wonder where this secret source of calcium originates. The
simple answer - from their own bones (primarily their rib cage). Since only the
healthiest males will be able to afford such a large diversion of resources, an
impressive set of antlers is also an impressive pedigree for parenthood.

During the autumn rut,
the individuals with the largest antlers (generally matched with the toughest
temperament) have an advantage when it comes to competing for mates. While
a large pair of antlers means mating priority, it does have its disadvantages.
The battle for supremacy can use up summer stores of energy, leaving them in
poor condition at the onset of the long winter. Being the most successful stag
may result in their perishing during the long mountain winter.

While only male deer, elk and moose grow antlers,
caribou are unique in that both males and females go through the annual process
of antler growth, just at different times of year. Male caribou grow antlers
during the summer, use them to compete for mates, and then shed them. Once the
rut ends, the females grow a short spike antler. This allows the females, who
must divert resources to reproduction during the time of year when food is
scarce, to outcompete the stags for limited winter food sources.

How Do Antlers Grow?

Antlers begin as bony growths
covered with skin and hair (velvet). They grow at incredible rates, with
the immense racks of deer, elk and moose growing in just 3 to
4 months. This makes them one of the fastest growing
living tissues.

After the antlers have reached
their maximum size, blood vessels at the base close down causing the skin to dry
up and peel off. The owner assists this process by rubbing against trees. In
many areas, you can see these rubbings as the thin bark of the aspen trees is
rubbed off along with the velvet. As the velvet peels away, they eat the newly
removed skin. Once the velvet is gone, only the hard bony
core remains as a formidable weapon in the annual mating game.

In order to grow these huge
racks, deer and elk must eat upwards of 50 kg of calcium each season. This is
quite a feat when their diet is composed of plant material. Prehistoric elk had
racks that measured upwards of 2 metres in size and would dwarf today's much
smaller descendents.

Going, Going, Gone!

When the mating game ends, it would seem to make
sense to shed them as soon as possible. For every kilogram of antler, the deer
must consume enough food energy to support the weight. This is even more
difficult during the harsh winter when food is not only of poorer quality, but
also more limited in nature. Deer, moose and caribou usually shed their antlers
by the end of December. Elk, on the other hand, are more social. They have found
a secondary purpose in helping the stags compete for limited winter food
supplies. This seems to outweigh the energy costs of carrying the antlers
around. Elk only lose their antlers in April or early May, just in time to grow
a new pair.

Prior to antler loss, the body begins to draw the
calcium back into the body. This leaves the antlers more brittle, and somewhat
more porous. A specialized layer of cells form near the base, adding to the
brittle character, until finally, the antlers fall to the ground, usually one at
a time, separated by a few hours or a few days. It is not uncommon at this time
of year to see deer with only a single antler during the interim period.

Antlers vs. Horns

Visitors often comment on the impressive ‘horns’ of the elk
stags wandering Jasper and Banff townsites. They are actually
referring to antlers. Horns are very different. True horns, like those
found on bighorn sheep, mountain goats,
bison and pronghorn, grow continuously throughout an animals life, and
cannot be replaced if damaged or broken off. The outer surface of horns is
composed of keratin, a substance similar to finger nails, and they are nourished
by blood vessels within the horn itself.

Antlers are essentially bones growing from the front of the
skull of the deer. Antlers are usually longer than horns, and have many branches. No
horned animal in the Rockies shows branching horns

The next time you marvel at the impressive
antlers on a large elk or moose, remember, they took only 3 to 4 months to grow!
They represent one of the great examples of adaptation and evolution in the deer
family.